3rd generation partnership project (3GPP) long term evolution (LTE) is an improved version of a universal mobile telecommunication system (UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.
The introduction of multiple carriers in 3GPP LTE results in the use of a plurality of serving cells. That is, the plurality of serving cells provides a user equipment with various services.
The number of usable serving cells among configured cells is not fixed but varies depending on user equipment's capability or a network condition. This is called activation/deactivation of the serving cell.
When the serving cell is frequently activated or deactivated, information related to the activated serving cell may be mismatched between the user equipment and a base station. For example, the base station deactivates the serving cell but the user equipment still regards the serving cell as the activated serving cell.
The mismatch may cause data loss or service quality deterioration.